1. Simulation of mixed traffic on a railway section
R.Vidyadhar, Narayan Rangaraj
Industrial Engineering & Operations Research, IIT Bombay
Soumya Dutta
Electrical Engineering, IIT Bombay
Ayush Agrawal
ITSPE, Hyderabad
- Corresponding author

2. Introduction Increased expectation of performance of railways
Faster traversal times
More trains to be handled
Variety of rolling stock and train types
Safe running, environmentally friendly and energy efficient  taken for granted
For multi-faceted operation, simulation → objective system performance as a whole
Even with dedicated freight corridors, many rail sections will have mixed traffic
Performance on such sections is of interest

3. IIT Bombay Rail Simulator
Rail traffic simulator at IIT Bombay – (with IRISET, RITES, RDSO support) – complete traffic analysis
Has been used for analysis of Mumbai suburban and other test sections
Intended as a line simulator for
Line capacity calculations and Timetabling
Comparative analysis of performance (e.g. auto signalling, fast turn-outs, easing of speed restrictions)
Impact of different traffic mixes on a given section
Needs extension to accommodate terminal/junction operations and eventually network wide operation

4. Construction of Test Case
Allahabad division: ALD - Mughalsarai taken as a detailed test case
Data as of mid-2015 taken for purpose of study
Automatic signaling MGS-Chunar, Absolute block working Chunar-Mirzapur, Automatic signaling Mirzapur ALD
Chunar-Mirzapur has been upgraded to Auto signaling since then
Approximately 50 passenger trains a day run in each direction, as per the working timetable (including allowances and planned overtakes)

5. Test section – Cont’d
Three types of passenger trains - max speed 130 kmph, 110 kmph and 100 kmph considered
A variable number of freight trains run with different firing times to get an estimate of the number that can be run effectively
Raw capacity – based on critical section
Mixed capacity – based on simultaneous handling of passenger trains and freight trains with reasonable traversal times
Thumb rule – Average traversal time of freight trains that are operated should not exceed twice the free running times of a single (typical) freight train on the section (in the presence of scheduled passenger trains)

6. Parameters considered
From recent notifications [1] & [2] Gatimaan express is a semi high speed train with max speed 160 km/hr
Acceleration & Deceleration of Gatimaan train taken as 0.2 m/s^2
Acceleration & Deceleration of Freight train taken as 0.05 m/s^2
With the increase in axle load, freight train max speed considered in the range kmph
MGS-ALD : 150 kmph, free running time 2-3 hours

7. Test Results Pass’ger train Speed kmph Freight Train speed kmph
Raw Capacity
Mixed Capacity
Average Traversal Time (HH:MM)
130 60
123 77
05:21
160 70
05:36 45
112
05:26 57
05:16
**For test case 2 & 4, max. speed of 130 kmph scheduled trains are replaced by 160 kmph.

8. Modified Test Cases
Initial computations show that introduction of semi high speed passenger trains and high axle freight train (increase in speed differentials), overall freight carrying capacity decreases
To improve mixed traffic capacity, as per recent circular [4] regarding “right powering”, freight train’s acceleration has been increased (doubled)
Availability of locomotives?
With this new change in parameter, a test has been conducted for the mixed traffic scenario

9. Modified Test Results
Parameters
Before Modification
After Modification
Freight Acc. & Dec. m/s^2
0.05
0.1
Scheduled Train max. Speed (kmph)
160
Freight Train max. Speed (kmph) 45
Mixed Capacity 57 72
Average Traversal Time (HH:MM)
05:16
05:29
With right powering, capacity can be increased in mix traffic situations

10. Some inferences
Auto signaling very effective for homogenous traffic (e.g. Mumbai suburban or freight-only sections)
Less effective (capacity) for mixed traffic
In mixed traffic scenarios, often at the cost of traversal times
Can lead to congestion and high traversal times
Safety not a concern, with modern technology
Parameters for overall system benefit, e.g. increasing speeds without suitable powering of locomotives not likely be beneficial

11. Conclusions
Indicative analysis and inferences, from available sources/data and discussion with Indian Railways
Formal study needs to be done for complete validation and policy implications
Many agencies capable of co-operating on this analysis, including RDSO, CRIS and RITES (+ external consultants?) and interaction with academic institutions and researchers is very desirable
Thank you!

12. References
Article: India Launches first 160 kmh semi high speed train, Source: Railway Gazette, Link: view/view/india-launches-first-160-kmh-semi-high-speed-train.html.
Running of railway stock 2016, Circular No: 2016/CEDO/SR/01, Indian Railways, Link: =0&id=0,1,304,366,526,626,1645.
Axle Load, Source: Wikipedia, Link:
“Mission Raftaar” Right Powering of Freight trains Circular, Link: =0&id=0,1,304,366,1762